Plepler addressed the hacking incident in an internal email to the staff on Wednesday, reports Variety.com.

He wrote: "Many people have expressed particular concern about our e-mail system. At this time, we do not believe that our e-mail system as a whole has been compromised, but the forensic review is ongoing."

Earlier this week, news broke that hackers had broken into the company's computer networks and possibly stolen as much as 1.5 terabyte of data. The hackers proceeded to leak unreleased episodes of a handful of shows and promised to leak more data in the coming days.

Plepler's email was apparently meant to calm the nerves of the network's staff, and address what he called "an enormous amount of speculation in the media".

"It is important to understand that, as is often the case, things you read may very well not be true," he wrote.

Plepler also wrote that HBO was working with an outside firm to provide free credit monitoring for its employees, suggesting that personal information of employees may have been part of the leak.